Kyle Busch led the most laps of Sunday's Auto Club 400 and escaped with a win after leaders Joey Logano and Denny Hamlin crashed on the last lap. / Gary A. Vasquez, USA TODAY Sports

by Jeff Gluck, USA TODAY Sports

by Jeff Gluck, USA TODAY Sports

FONTANA, Calif. - Denny Hamlin was released from Loma Linda University Medical Center late Monday with a compression fracture in his lower back.

He had remained there overnight after being airlifted after a hard single-car crash on the final lap of Sunday's Auto Club 400.

The compression fracture -- which occurs when a vertebrae in the spine collapses -- can occur in healthy people who suffer a vertical shock to the area.

Austin Peyton, Hamlin's day-to-day business manager, told USA TODAY Sports that Hamlin will fly home to North Carolina for further evaluation by Dr. Jerry Petty of Carolina Neurosurgery & Spine Associates later this week.

Peyton said it is undetermined whether surgery will be needed or whether Hamlin might miss any races.

Hamlin has previously struggled with back problems; his father also has had a bad back, and Hamlin believes it's genetic. His back occasionally locks up, and he's undergone rehab and injections to try and make it better.

It's unclear whether the Fontana injury is connected to or exacerbated by Hamlin's existing back problems.

Hamlin was awake and alert in the infield care center before being transported Sunday, but was taken to the hospital after complaining of lower back pain. A helicopter was used due to post-race traffic.

Hamlin was helped from his car after the hard hit and seemed to collapse outside his car after he had pulled the window net down. He was taken by ambulance to the infield care center, where crew chief Darian Grubb hurried inside to check on the driver.

The feud between Hamlin and Logano started at this season's Daytona 500, where Hamlin was unhappy with the way he claimed his former Joe Gibbs Racing teammate clogged traffic near the end of the race. In a Twitter message to Brad Keselowski, Hamlin referred to Logano as a "genius teammate."

"It's frustrating," Logano said. "We've got a freaking genius behind the wheel of the 11 car. Probably the worst teammate I've ever had. So I learn that now. He chose to run into the back of me. So whatever. I have a scorecard. I ain't putting up with that."

That escalated into a war of words on Twitter afterward with Logano writing, "Hey @dennyhamlingreat job protecting that genius brain of yours by keeping your helmet on." Hamlin responded with "Why's that ... what would u do?", prompting @joeylogano to reply "Show you some love and appreciation." Hamlin responded, "Need my address?" And then: "Last time I checked he had my cell and direct message button to choose from if he's got a problem ... Otherwise hush little child."

In one-sentence responses, Logano vowed to race Hamlin "the way he raced me" and said there won't be any resolution "until anyone says anything to me personally."

"I haven't gotten a phone call, so he can tell you whatever he wants, right?" Logano said to reporters.

Minutes earlier, Hamlin told the media he regretted questioning Logano's driving ability because "I didn't need to give my opinion on that; I think it was kind of a low blow."

When the two were teammates at Joe Gibbs Racing, Hamlin said, they clashed on the racetrack several times but it was kept out of the spotlight.

"It never really was public, but we had times where it was like, 'Hey, why'd you race me that way?' or vice versa," Hamlin said. "I think I had just as much disappointment as him on the racetrack as teammates as he had in me. I think it was an even shake there.

"Off the racetrack, we'd see each other on the racetrack in Monday morning meetings and be like nothing ever happened."

It was Busch's first win of the season after he had flirted with winning several times in the first four races.

"They forgot about me. I knew they were going to," Busch said. "It's so fun to come out here and perform like this."

Busch acknowledged that he probably wouldn't have pulled out the victory if not for Logano and Hamlin's heated battle, which he called "golden."

"I was just thinking, hopefully I can get by before they wreck. I can make this happen," Busch said.